Hydrogen holds a substantial promise as a plentiful, clean-burning fuel that may even replace gasoline. The advantage of reducing the amount of greenhouse gas will become more important with time. The combustion of hydrogen produces water.
There are a number of systems for the generation of hydrogen for a variety of purposes. Estimates suggest that more than nine million tons of hydrogen is produced annually. Hydrogen is generated by a chemical reaction between a reactive metal fuel such as aluminum, magnesium, or lithium, and alloys or hydrides of these and similar reactants, with an “oxidizer” such as hydrogen peroxide, Freon, sulfur hexafluoride, water, and others. Molten metals are also used as one of the reactants. Hydrogen generating materials have been investigated including LiH, LiAlH4, NH3 Al, Mg, MgH2, and LiBH4. These materials are often reacted with water to generate hydrogen.
In many cases the most economical and efficient hydrogen generators are those that react water vapor from store liquid water with a chemical hydride. The water is stored at ambient temperature and converted to water vapor for the reaction with the chemical hydride. The main problem with these hydrogen generators is that they cannot operate below 0° Celsius with frozen water or ice, without disrupting operation or risking damage to the generator due to expansion as the liquid water changes to a solid.
It would be of advantage in the art if hydrogen generators that use liquid water converted to water vapor and a chemical hydride could operate where the water is stored at temperatures below 0° Celsius.
Yet another advantage would be if such a hydrogen generator would retain the advantages of stored liquid water producing water vapor for reaction with a chemical hydride reaction to generate hydrogen without the concern for colder temperatures.
Other advantages will appear hereinafter.